1. Field of the Invention
The present invention relates to poly(trimethylene terephthalate) (PTT) yarn, and more particularly to a method of producing bulked continuous filament PTT yarn useful in the fabrication of carpets and pile fabrics.
2. The Prior Art
It is well known to use bulked continuous filament PTT yarns in fabricating carpets and pile fabrics due to the natural stain resistance displayed by PTT. As disclosed in U.S. Pat. No. 5,645,782, such yarns are conventionally produced by a single spin-draw-texturing procedure wherein molten PTT polymer is extruded through a spinneret to form PTT filaments, the filaments are cooled by means of air flowing perpendicularly to the filaments and then coated with a spin finish, the coated filaments are then heated and drawn between a pair of feed rolls and a pair of draw rolls, thereafter textured and finally wound up. However, since the filaments are drawn and textured immediately after being spun, the PTT filaments cannot be combined with other filaments, e.g., so as to provide a multicomponent finished product. In this regard, it is often desirable to combine PTT yarns with natural, delustered or colored yarns, antistatic yarns, marker, signature or other novelty yarns, or yarns for producing antimicrobial, flame retardancy, stabilization, or other functional enhancements.
Conventional two stage processing routes involve melt spinning an undrawn yarn in a first discrete step and then drawing and texturing the yarn in a second discrete step. However, PTT yarn physically ages. This aging phenomenon occurs at ambient temperature with any polymer that is essentially amorphous, or which has been quenched from molten state into an essentially amorphous state at a temperature that is below and close to the glass temperature of the polymer. This aging phenomenon causes essentially amorphous PTT yarn to become extremely brittle within a few hours after spinning, such that subsequent handling and processing results in filament breakage and damage.
EP 0 745 711 A1 discloses a process for forming bulked continuous filament PTT yarn wherein PTT polymer is melt spun through a spinneret into filaments, cooled with cold air, converged into a yarn, coated with a spin finish, drawn a first time between a feed roll and a first draw roll to achieve a draw ratio of 1.05 to 2, then drawn a second time between the first draw roll and a second draw roll to achieve a draw ratio of at least 2.2 times that of the first draw ratio, and then wound up. The drawn yarn can be textured before or after being wound up. Carpets fabricated in accordance with this invention have reasonably good stain resistance; however, their wear characteristics are only fair.
The present invention is directed to a process for producing bulked continuous filament PTT yarns wherein the yarns can be combined with other types of yarns in a two stage process, and wherein carpets made from such yarns have unexpectedly improved wear resistance.